Kamailio in-dialog request from C code

indialog_request.c

static int requestWithinDialog(char *callId, char *cseqNum, char *fromTag, char *toTag,
                               char *method, char *ruri, char *from, char *to, char *headers,
                               txCallback *callbackHandler, void *callbackParam) {
    LM_DBG("Call > requestWithinDialog\n");
    LM_DBG("Creating new %s request: fromTag: %s, toTag: %s, cseqNum: %s, callID: %s\n",
            method, fromTag, toTag, cseqNum, callId);
            
    uac_req_t uac_r;
    str methodStr = {method, strlen(method)};
    str headersStr = STR_NULL;
    if (headers != NULL) {
        headersStr.s = headers;
        headersStr.len = strlen(headers);
    }
    str bodyStr = STR_NULL;

    set_uac_req(&uac_r,
                &methodStr,               // method
                &headersStr,              // headers
                &bodyStr,                 // body
                NULL,                     // dialog
                TMCB_LOCAL_COMPLETED,     // cb_flags
                callbackHandler,          // transaction_cb
                callbackParam             // cb parameter
    );

    str callIdStr = {strdup(callId), strlen(callId)};
    str ruriStr = {strdup(ruri), strlen(ruri)};
    str toStr = {to, strlen(to)};
    str fromStr = {from, strlen(from)};
    str fromTagStr = {fromTag, strlen(fromTag)};

    ///////////////////////////////////////////////////////
    // [Copy-paste START] TM module, uac.c -> req_outisde()
    ///////////////////////////////////////////////////////

    // generate_callid(&callid);
    // generate_fromtag(&fromtag, &callIdStr);
    int cseq = atoi(cseqNum);
    cseq = cseq + 1;

    if (tmb.new_dlg_uac(&callIdStr, &fromTagStr, cseq, &fromStr, &toStr, &uac_r.dialog) < 0) {
        LM_ERR("Error while initialising dialog with existing dialog parameters\n");
        return -1;
    }

    // Set dialog toTag
    uac_r.dialog->id.rem_tag.s = shm_malloc(sizeof(char) * (strlen(toTag) + 1));
    strcpy(uac_r.dialog->id.rem_tag.s, toTag);
    uac_r.dialog->id.rem_tag.len = strlen(toTag);

    if (ruriStr.len > 0) {
        uac_r.dialog->rem_target.s = ruriStr.s;
        uac_r.dialog->rem_target.len = ruriStr.len;
        /* hooks will be set from w_calculate_hooks */
    }

    //if (next_hop) uac_r->dialog->dst_uri = *next_hop;
    tmb.calculate_hooks(uac_r.dialog);
    ///////////////////////////////////////////////////////
    // [Copy-paste END]
    ///////////////////////////////////////////////////////

    int ret = tmb.t_request_within(&uac_r);

    ret = (ret >= 0) ? 1 : -1; // Returning 1 if success, -1 otherwise
    LM_DBG("requestWithinDialog completed with exit code: %i\n", ret);
    return ret;
}